Fold3 is an online repository for original historical documents, combined with the ability for users to make comments, annotations, and upload their own documents. The focus of Fold3 is to be a comprehensive collection of U.S. Military records. Some areas of Fold3 are free to use, while others can be freely searched and then viewed with a paid subscription.

The purpose of the site is to have links to all online city directories in one place, listed by location and in date order. It is meant to be used as an aid to genealogists, historians, and other researchers. Included are county, rural, business, professional and other directories.